The present invention is directed to a plasma torch for micro-plasma welding which torch has a hollow cylindrical torch housing, an electrode supported at one end of the housing and insulated therefrom, a plasma jet or nozzle provided with a cooling chamber arranged adjacent the electrode, an inert gas jet or nozzle arranged concentrically around the plasma jet and various connections and lines for supplying plasma gas, inert gas, welding current and also tubes and lines for delivery and removal of a cooling agent to the plasma nozzle.
A plasma torch which has a cylindrical housing having a structure for supporting an electrode in the housing and insulating it therefrom and having a plasma nozzle or jet mounted on one end of the housing adjacent the end of the electrode, with an inert gas nozzle or jet being disposed concentrically to the plasma jet is known and an example is disclosed in German Letters Patent No. 1,806,858. In this known type of torch, which is usually used in micro-plasma welding, the electrode is a pin-shaped electrode, which is relatively thin and generally has a pin diameter of about 1 mm. Usually the design is such that the tip of the electrode will project into a funnel-shaped widening of the plasma channel of the plasma jet or nozzle with the funnel-shaped widening being provided for reasons of gas flow dynamics. However, since on the one hand, a stable focusing of the arc plasma cannot be achieved with this type of torch and, on the other hand, the torch is subjected to very high wear, it has been proven that the plasma torches of this type are not suitable for employment in a series manufacturing process. Since no defined focal spot is present in the torch, the unstable focusing of the plasma is caused by the flickering of the pilot light arc.